The present invention relates to an IPv4-IPv6 multicast communicating method and an IPv4-IPv6 multicast communicating apparatus in a communications network system. More particularly, it relates to a method and an apparatus for implementing the multicast communication between an IPv4 terminal using IPv4 (i.e., Internet Protocol Version 4) as the communications protocol and an IPv6 terminal using IPv6 (i.e., Internet Protocol Version 6) as the communications protocol.
As one example of the methods for implementing the communication between the IPv4 terminal and the IPv6 terminal, there can be cited a technology disclosed in U.S. Pat. No. 6,118,784 (JP-A-11-55319). This technology allows the communication between the IPv4 terminal and the IPv6 terminal in the following way: An IP address conversion table for managing the correspondence between an IPv4 address and an IPv6 address is created using DNS (i.e., Domain Name System) protocol extending technology in an apparatus located halfway in the communications path. Then, based on the IP address conversion table, an IPv4 header-IPv6 header conversion is executed, thereby allowing the communication to be implemented.